Did I buy a lemon?! "lifan 148cc"

[andrewmac805]

My first mini bike, bought at night, without a test ride (due to flat tire and darkness!). Sounds like a recipe for disaster!



Alleged by the seller: 148cc pit bike all good to go.... NAAAT!

Looks cool! Once I replaced the inner tube I took it for a spin. It bogs really bad on full throttle. Took the carb off (mikuni 26 672u) and cleaned it with carb cleaner (wasn't dirty), set the air fuel screw to 1.5 turns out. Still bogs on acceleration. Turned it out to 2.5 turns, still bogs.

Checked the timing marks, were good, adjusted the valve clearances (.003" intake and .004" exhaust), oil fell out the exhaust valve so changed the oil with diesel oil that I use in my 1980's street bikes.

That's when I noticed this cut wire:

Near the top right of the photo above the sprocket. Does anyone know what it's for!? Also noticed the lifan engine is stamped with 124cm3 on it!

Ordered a new spark plug, wire, cdi and uni filter (original had torn boot). They will all arrive in the new year.

I guess now that it's jetted wrong? How do I go about experimenting with jets and where's the cheapest to buy them?

Any advice is appreciated. Or where to find an exposed diagram or fsm for the lifan engine.

Thank you!

 

[gottagetacheaperhobby]

No need to stress about the cut wire, thats a gear position sensor, useless to you...
The mikuni is a china copy, nothing flash but better than the crap that they come with stock. Not sure about which jets would be a good starting point as i have always turfed them and gone for an oko or keihin..

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[motodevo]

As mentioned, that carb isn't the best option. Pretty sure you'll find its only a 124cc lifan. If the engine number starts 1p54fmj its a 124cc (the 54 stands for a 54mm bore)

 

[andrewmac805]

Thanks for the replies guys! Yeah I was thinking more about that wire and thought it would be a neutral light or something like that.

I guess I'll just slowly start swapping everything out. It has fast ace upside down forks and a fast ace rear shock. I'm pretty sure those can be rebuilt too.

Any tips on where to get cheap jets?

 

[low_rb]

All you can really do is play with the needle height until you get some jets.
DHZ sell them at $5 each.
No one ca make a suggestion on what ones to buy until you pull the carb off and find out which ones are in it.

 

[21Guns]

Order a #15 and #20 jets to play with. Im running a #20 in my lifan with the same carb. As for bogging down check your crank case breather hose. Mine split and was causing similar problems.

 

[rotn50]

Make sure your idle is not too low. Sometimes a slightly higher idle can eliminate similiar issues. And run an ngk c7hda plug.

 

[headsmess]

the clutch is the biggest giveaway that that there is a lifan or similar 125, or 119 when you actually do the math on bore and stroke. 1pfm52...or 4?

the 54 is a genuine 125, and usually have big valves in them. look for a triangle sort of thing cast into one of the fins on the head, thats a good sign its got the big valves. theyre pretty good little engines, but def not a 148-150 like you were told.

adjusting the screw on the carb wont do jack as it only adjusts idle air mixture.

jets...you could try a jaycar or similar and get some microdrills and a pinchuck, simply solder them up and drill them out a few sizes smaller, then work your way up to bigger sizes until it feels "right". bunnings used to sell the microdrills, havent checked in ages. a $12 set is better value than buying several different jets and only using 1 in the end...

other option is to find some really fine wire, like out of a set of headphones. solder one strand into the jet (just poke it in and tack the end of it to the edge of the jet, dont solder the hole!) at a time, test, add another strand, etc... until you go too far, then pull the last two strands out again. easy to do and the jet doesnt change size...

only wires to worry about from the engine is the black(or white)/red, black(or white)/blue and green. that one above the sprocket is, yep...the neutral indicator. ensure green is earthed well (no paint or rust!) same with the coil.

a split breather hose wont do jack either, as it still lets the engine breath. a blocked breather though...well...


make sure its got oil!

idea to check the valve clearances.

 

[andrewmac805]

Have a #20 pilot jet and #100 main jet. Put the needle to the lowest setting (more needle sticking up in the sleeve) and it was still bogging.

Ordered some new main jets. Tried 95 and 90 so far and still no luck. So continue down the line now. Only have an 88 and 86 left.

Installed one of those blue "racing" cdi's, a new spark plug wire and ngk CR7HSA plug.

My crank case hose is just a hose from what I can see, doesn't have a cap or anything. So don't see how that being cracked would affect anything (doesn't look cracked anyway).

Also put a new uni filter on it and oiled the foam.

Adjusted the valve clearances to:
Intake: .003" or 0.08mm
Exhaust: .004" or 0.10mm

 

[andrewmac805]

pretty conclusive that it's NOT a 148cc.

Has been dressed up a little tho. Keeps leaking oil from the exhaust valve cover. Is it supposed to have a gasket around it?

New filter and cdi (as best as I can attach it)

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[andrewmac805]

O yeah, it idles great

 

[GROMMER]

Did you ever figure out the issue?

 

[rotn50]

pretty conclusive that it's NOT a 148cc.



Has been dressed up a little tho. Keeps leaking oil from the exhaust valve cover. Is it supposed to have a gasket around it?



New filter and cdi (as best as I can attach it)

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**** mate. There is your issue. A 30mm carb on a 125. That's way too big. A mikuni copy 19mm will run that beautifully. Biggest I'd go on that particular motor is the mikuni copy 26mm. That 30 mikuni will forever bog unless you turn the idle up so it's padt the idle jet usage point.

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[andrewmac805]

**** mate. There is your issue. A 30mm carb on a 125. That's way too big. A mikuni copy 19mm will run that beautifully. Biggest I'd go on that particular motor is the mikuni copy 26mm. That 30 mikuni will forever bog unless you turn the idle up so it's padt the idle jet usage point.

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You are a smart man!

I saw a mikuni vm22 for cheap on Amazon and plopped that little bad boy in and I was whiskey throttling my way around the back yard lol!

Now the issue is it's blowing oil out to the exhaust, not excessive, but not good!

Guess I need new piston rings!

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[coolmodee01]

or valve stem seals

 

[rotn50]

You are a smart man!

I saw a mikuni vm22 for cheap on Amazon and plopped that little bad boy in and I was whiskey throttling my way around the back yard lol!

Now the issue is it's blowing oil out to the exhaust, not excessive, but not good!

Guess I need new piston rings!

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Is the inside tip of the muffler wetting from oil. Does it blow smoke at idle and WOT? And what colour? (Whitish, blueish) Check your crank breather at the rear top of the engine. This can cause whitish smoke if blocked which leads to blowby and pushing out of seals, mainly the sprocket seal.

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